GPS with no cell service

It must have cell phone data to work.

It can give you it's version of co-ordinates without a cell tower, and if you know the offsets to apply, you can apply them to an ordinance survey map with a compass and calculator.

But it won't plot a solution home or the other stuff it can do, a Garmin GPS will guide you in the direction of there you want to go, even if off the map ~~ try it for yourself with the iPhone, off the map and with no service.

icebike wrote:
It has a real gps and will work where there is no cell service.

Any statement to the contrary is just wrong!

AND an error message like cannot locate current position!

For the most part, iPhone tends to be more accurate when working, Garmin like GPS systems are often wrong as they also use 'predictive' logic and may place one on nearby roadways when one is in a field or unmarked shopping centre.

icebike wrote: No maps, no display..

GPS worked fine for me with no cell coverage. I just dropped pins on boundary lines and other points as we walked through the woods and used the pins later to see where we were via aerial. Pretty handy.

{quote:title=evdh wrote:}When I put it in AirPlane mode there is no information available, not in googleMaps, not in other apps like GPS Kit. Just test it for yourself if you have an iPhone. It can be that when in AirPlane mode the GPS unit is also turned off. I don't know that.{quote}

Now I know...

When airplane mode is on, no cell phone, radio, or Bluetooth signals are emitted from iPhone (and GPS is not available with iPhone 3G).

I found this in the following artical : http://support.apple.com/kb/HT1355

Go outside.

The GPS chip requires a clear view of the sky. Inside it relies on cell tower information to come up with an approximation.

You, Mr Bons, have posted three times in this thread and every single one of them have been dead wrong and/or totally nonsense.

Assisted GPS does NOT mean that it has no GPS receiver. It most certainly DOES have a GPS receiver.

It uses the Infinion PMB252 Hammerhead Gps receiver: http://i.cmpnet.com/techonline/uth/pmiPhone_boardtopBIG.jpg

See article: http://www.techonline.com/product/underthehood/209000013?pgno=1

That chip is described here: http://www.infineon.com/cms/en/corporate/press/news/releases/2004/132119.html

The Assisted feature of this chip allows Three things:
1) Best Guess location (based on tower location data) when inside buildings, where satellite signals do not penetrate.
2) Faster Satellite lock when outside, reducing lock time from several minutes to seconds.
3) Ability to use vastly weaker GPS signals when inside a building allowing for precise locations even in challenging environments.

In the absence of cellular tower data, satellite acquisition is slower, but with a clear view of the sky it will be quite accurate within 3 minutes.

*Now PLEASE STOP posting nonsense and Slander about APPLE products and do JUST A LITTLE research.*

This is not my experience. On a recent trip abroad I had data-roaming off (for obvious reasons) and with no access to an open wi-fi network no GPS position is ever found. I use imarkmyspot which does not use maps, just finds your position. But it does not work without a data connection.

But it doesn't. See my post above.

Could it be possible that perhaps the app itself is coded in such a way that when opened, it "needs" to detect a data connection in order for it to work correctly? IIRC, there is at least one GPS app that will run w/o first needing to detect a data connection (e.g., WiFi, 3G, EDGE, etc.)...apparently, the one you're using isn't it.

Yes, this was my first thought as well. I'll need to get some more GPS apps to test them the next time I travel outside of my home country.

Me too. My Twitter app picked up the lat/long from the GPS and 10 mins later when back in service, I tweeted the co-ords.

Not in my experience. My App (Twittelator) successfully asked if it could get the location form the iPhone and got the correct lat/long from the device. This was 10 mins after signal from any cell network or wifi was lost and 10 mins before we got signal again. I then "twittered" the post when back in 3G cellnet range.

So I clearly demonstrated to myself that with no phone or wifi network available and outdoors, the iPhone does offer a GPS coordinate to applications that request it.

See the twitpic I took which embedded the link to google maps showing the received lat/long from the iPhone GPS with no Cell coverage, outdoors. (This is a Twittelator function) http://twitpic.com/dd84 and I can confirm the location to be correct.

In contrast, here was a twitter where the application got both a GPS lat/long and had cell net 3G access http://twitpic.com/dcyc

is everyone here using the NEW 3G or have some just been inputting generic iphone responses???

i agree with ice and if you read the technical data you will see the new and old iphones operate differently when it comes to the GPS.

bons... it sounds like you keep describing the old iphone's functionality when it comes to the GPS... which was software driven because there was not a chip on the board.

I'd like to ask a question to elaborate on this topic. I've been in the woods a lot lately and the GPS jumps around quite a bit, and I frequently have the lowest cellular signal possible without actually having "no signal". Thank you icebike for the links regarding the infineon chip in the iphone 3g, could you let me know generally how it compares to other major GPS chipsets? For example, the only other chip I have experience with, the SirfStar III that is in my car GPS unit... how does the iphone's infineon chip compare with that in terms of accuracy and ability to detect weak signals? Do you know how many satellites the iphone's chip tracks at once to determine the signal?

You seem very knowledgeable about this hardware in the iphone, please elaborate a bit more and give me a good comparison between it and the SirfStar setup in my Magellan.

Cheers!

Antenna is a big factor for GPS. A dedicated GPS like Magellan or Garmin has a good size antenna to help maintain a satellite lock. In the woods with a weak cell signal and no clear line of sight to the sky, the GPS on the iPhone is going to have a hard time maintaining a position.